Conventional lithography technology for manufacturing semiconductor devices includes double patterning technology by ArF liquid immersion exposure, EUV lithography, and nanoimprint. The conventional lithographic technique suffers various problems such as increase in cost, reduction in throughput, with miniaturization of the pattern.
Under such circumstances, application of self-assembly (DSA: Directed Self-Assembly) to lithography has been explored. Since self-assembly occurs due to the spontaneous behavior called stable energy, and a pattern with high dimensional accuracy can be formed. In particular, periodic structures of various shapes of several nanometers (nm) to 100 nm can be formed by using a micro phase separation of the high molecular block copolymer with a simple application and annealing process. The shape is changed to spherical (sphere), columnar (cylinder), layered (lamella), depending on the composition ratio of the high molecular block copolymer. By changing the size depending on the molecular weight, a pattern such as, dot pattern, holes or pillar pattern, line, of various dimensions can be formed.
In order to form a desired pattern in wide range using DSA, it is necessary to form a guide structure which controls the genesis location of the polymer phase formed by self-assembly. As the guide structure, a structure having depressed portions and projected portions is used; and a physical guide (grapho-epitaxy) forming a micro phase separation pattern at the depressed portion, and a chemical guide (chemical-epitaxy) which controls the position of micro phase separation pattern based on the difference between the surface energy of patterns, which are formed at the lower layer of the DSA material, are known.
When forming the micro phase separation pattern by using such type of guide, by applying self assembled material on a surface energy controlled base film, the effect of the surface energy in the region separated from the base film is low and the self assembled material does not phase separate periodically (regular) in a uniform manner. This happens because the periodic phase separation is in a metastable state and if energy is not received from the surroundings, the self assembled material becomes separated randomly. Due to this, conventionally, at the time of formation of regular micro phase separate pattern, the film of the self assembled material is made sufficiently thin so that the effect of the surface energy of the base film is dispersed. However, sufficient fabrication tolerance is not obtained in the micro phase separation pattern of such thin films